<aside> ⚠️ This will also stop UWP apps and games from the Microsoft Store (like Minecraft Bedrock) from accepting controller input. Do not use if you're playing games from there.
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Windows 10 makes it such that guest's controllers can move through the start menu, which can be very annoying. Below is a workaround that consists of installing an older Xbox controller driver to remove that behavior.
Save this link as a .reg file and run it, then restart the computer. To re-enable, edit the file and change the last number to a 1, and run that.
I couldn’t get this to work personally. If it fails for you, fall back to the Windows 10 steps.
Do the following steps on the host you want to disable the behavior on. You should get as many guests as you plan to play with so you can configure all the controller slots right away, and ask them to press buttons for their controllers to show up. If you only configure it for 2 guests for example, and a third guest joins your stream later, they will still be able to control the start menu.
After installing it in each of the controllers, restart the computer to apply the changes